Sneaking
Hiding, disguising or delaying information that, if the person saw it in time, would lead them to decide differently (Gray et al., 2024, p. 17).
Sneak into basket
In SERNAC's 2022 report: “Colarse en la cesta”.
What it is. Hides information in order to add something to the cart that the person did not ask for. As a result, they believe they are buying only what they chose and end up paying more (Gray et al., 2024, p. 17).
What you see
- A product or service in the cart that you did not add: a greeting card next to a bouquet of flowers, an insurance plan next to a laptop (Mathur et al., 2019, p. 13).
- Checkboxes, already ticked on an earlier step, that add something to the order (Mathur et al., p. 13).
How to check. Add a single product and read the cart line by line before paying. Go back through the previous steps and look for ticked boxes you did not tick.
Evidence. Mathur et al. found 7 cases (Table 1, p. 12). In Chile, SERNAC recorded it in 10 stores (2021, p. 16). But its examples are something else: credit life insurance (seguro de desgravamen) ticked by default in loan simulators (pp. 25–26). In Gray's ontology that is a bad default, and it is just as easy to spot: check every option that comes pre-selected.
Can it be found by searching text? No. SERNAC left it out of its automated search because it needs manual review: simulating the purchase, looking at colors or reading the whole offer (2022, Table 3, p. 9).
Bias (hypothesis). Default effect, according to Mathur et al. (Table 1, p. 12).
Related: Pressured selling · Drip pricing or hidden costs
Drip pricing or hidden costs (drip pricing)
In SERNAC's 2022 report: “Costos escondidos”.
What it is. Hides information in order to show new charges, or the full price, only at the end. As a result, the person decides on a price that was not the real one, after having already invested time in the process (Gray et al., 2024, p. 17).
What you see
- Charges that appear on the last step: “service fee”, “handling fee”, delivery, tip (Mathur et al., 2019, p. 13; SERNAC, 2021, p. 27).
- A package price that changes when you confirm, with no explanation (SERNAC, p. 28).
How to check. Write down the price shown on the product page and compare it with the total on the last step before paying. Every difference should have been disclosed from the start.
Evidence. Mathur et al.: 5 cases (Table 1, p. 12). SERNAC: 6 stores (2021, p. 16).
Can it be found by searching text? Partly. SERNAC built 11 typical phrases for this pattern (2022, Table 3, p. 9); a phrase match is a signal to look closer, not proof.
Bias (hypothesis). Sunk cost fallacy, according to Mathur et al. (p. 13).
Related: Sneak into basket · Price comparison prevention
Obstruction
Making a task harder than it needs to be in order to dissuade the person (Gray et al., 2024, p. 17).
Roach motel
In SERNAC's 2022 report: “Difícil de cancelar”.
What it is. Makes it easy to get in and hard to get out: subscribing or creating an account takes one click, cancelling does not (Gray et al., 2024, p. 17).
What you see
- You subscribe or sign up on the website, but there is no button to cancel or to delete the account.
- The only option offered is to “pause” the membership, not cancel it. Chen et al. labelled this as forced action (2026, p. 8); for an auditor the symptom is the same: there is no way out.
How to check. Compare the two paths: how many steps and which channel it takes to sign up, and how many it takes to leave. If you cannot find how to leave in the interface, look in the terms and conditions: that is often where “by phone only” lives (Mathur et al., 2019, p. 21; SERNAC, 2021, p. 30).
Evidence. Mathur et al.: 31 cases (Table 1, p. 12). SERNAC: 2 stores (2021, p. 16).
Can it be found by searching text? Partly. SERNAC built 16 typical phrases for this pattern (2022, Table 3, p. 9); a phrase match is a signal to look closer, not proof.
Bias (hypothesis). Mathur et al. do not assign one (Table 1, p. 12).
Related: Forced continuity or hidden subscription · Glossary entry
Price comparison prevention
What it is. Puts up barriers so the person cannot compare prices, whether across sellers or across options on the same site. As a result, they cannot make an informed decision (Gray et al., 2024, p. 17).
What you see
- Similar products with different specifications and different discounts at the same time, which cannot be put side by side (SERNAC, 2021, p. 24).
- A “from” price in the listing that always belongs to the cheapest option, with many variants at different prices once you open it (SERNAC, p. 24).
- Text that cannot be copied (Gray et al., p. 17).
How to check. Try to compare two equivalent options. If you have to take notes by hand, open each one or work out unit prices to do it, there is a barrier. Whether the barrier is deliberate cannot be proven from the outside; record it as a finding with that caveat.
Evidence. Not among the types in Mathur et al. SERNAC: 7 stores (2021, p. 16).
Can it be found by searching text? No. SERNAC left it out of its automated search because it needs manual review: simulating the purchase, looking at colors or reading the whole offer (2022, Table 3, p. 9).
Bias (hypothesis). None of the sources in this guide assigns one.
Related: Drip pricing or hidden costs
Interface interference
Manipulating the interface to privilege some actions over others (Gray et al., 2024, p. 17).
Visual interference
In SERNAC's 2022 report: “Interferencia visual”.
What it is. Gives more visual prominence to the option that suits the company, where the options should look equal. As a result, the person does not compare properly or chooses without noticing the alternative (Gray et al., 2024, p. 18).
What you see
- The button that suits the company is large and colored; the alternative is gray or a plain text link (SERNAC, 2021, p. 22).
- An option that looks disabled but can be clicked (Mathur et al., 2019, p. 17).
- A discount inflated by adding in the value of a “free gift” (Mathur et al., p. 17).
How to check. Compare the options within the same decision: size, color, contrast and position. If one looks disabled, click it.
Evidence. Mathur et al.: 25 cases (Table 1, p. 12). Their method read only text and left style out (pp. 17 and 26), so that number is probably low for a pattern that is visual. SERNAC: 13 stores (2021, p. 16).
Can it be found by searching text? No. SERNAC left it out of its automated search because it needs manual review: simulating the purchase, looking at colors or reading the whole offer (2022, Table 3, p. 9).
Bias (hypothesis). Anchoring and framing, according to Mathur et al. (Table 1, p. 12).
Related: Confirmshaming · Pressured selling
Trick questions
What it is. Words a question confusingly, with double negatives or checkboxes that switch between accepting and declining, so that the person ticks the opposite of what they want (Gray et al., 2024, p. 18).
What you see
- “Uncheck the box if you prefer not to receive email updates” (Mathur et al., 2019, p. 17).
- A box for NOT receiving communications whose text opens by stating the opposite: “We would like to send you emails. If you do not wish…” (Mathur et al., p. 17).
How to check. Read every checkbox out loud and ask what happens if you tick it and what happens if you don't. Mathur et al. only count as a trick question an opt-out box that opens with an affirmative statement. Those that open by offering the opt-out (“Tick here to opt out of…”) are recorded separately, as concerning but not deceptive (note 9, p. 17).
Evidence. Mathur et al.: 9 cases (Table 1, p. 12). In Chile, SERNAC's 2021 report defines it (p. 9) but did not survey it. In 2022, SERNAC analysts who manually reviewed 360 pages found trick questions on 24 pages (Table 14, p. 18); the report does not say what criterion they used.
Can it be found by searching text? Partly. SERNAC built 7 typical phrases for this pattern (2022, Table 3, p. 9); a phrase match is a signal to look closer, not proof.
Bias (hypothesis). Default effect and framing, according to Mathur et al. (Table 1, p. 12).
Related: Forced registration
Pressured selling
What it is. Pre-selects or highlights the most expensive version of a product. As a result, the person does not see that a cheaper option would have served them just as well (Gray et al., 2024, p. 18).
What you see
- The most expensive option selected by default: the largest bouquet, the top plan (Mathur et al., 2019, p. 18).
- Pop-ups that, when you add something to the cart, offer “hot sellers” or “deals” and have to be closed before you can continue (Mathur et al., p. 18).
How to check. Check which variant is selected when you open the product page. If it is the most expensive one, note it. Also check whether a pop-up interrupts the way to the cart.
Evidence. Mathur et al.: 67 cases (Table 1, p. 12). SERNAC defines it (2021, p. 9) but did not survey it.
Can it be found by searching text? Partly. SERNAC built 7 typical phrases for this pattern (2022, Table 3, p. 9); a phrase match is a signal to look closer, not proof.
Bias (hypothesis). Anchoring, default effect and scarcity bias, according to Mathur et al. (Table 1, p. 12).
Related: Sneak into basket · Visual interference
Forced action
Requiring an additional action, such as signing up or handing over data, before the person can continue (Gray et al., 2024, p. 18).
Forced registration
In SERNAC's 2022 report: “Inscripción forzosa”.
What it is. Makes the person believe that signing up or creating an account is required for an action that does not need it. As a result, they hand over data that was not necessary (Gray et al., 2024, p. 18).
What you see
- “Debes registrarte para continuar tu compra” (“You must sign up to continue your purchase”), with no guest checkout (SERNAC, 2021, p. 17).
- A sign-up window that appears when you add to cart or after browsing for a while, with no close button (Chen et al., 2026, p. 8).
- A single checkbox that bundles accepting the terms with agreeing to receive marketing (Mathur et al., 2019, p. 22).
- Personal data requested too early, for example the RUT (Chile's national ID number) just to simulate a loan (SERNAC, p. 18).
How to check. Try to complete the task without an account. If a window appears, look for a way to close it without signing up. Ask what data each step actually needs.
Evidence. Mathur et al.: 6 cases (Table 1, p. 12). In Chile it was the most frequent: 30 stores (SERNAC, 2021, p. 16).
Can it be found by searching text? Partly. SERNAC built 34 typical phrases for this pattern (2022, Table 3, p. 9); a phrase match is a signal to look closer, not proof.
Bias (hypothesis). Mathur et al. do not assign one (Table 1, p. 12).
Related: Forced continuity or hidden subscription · Trick questions
Forced continuity or hidden subscription (forced continuity)
In SERNAC's 2022 report: “Suscripciones escondidas”.
What it is. Keeps a subscription charging, or turns something presented as a one-off payment or free trial into a recurring one, without the person noticing (Gray et al., 2024, p. 18).
What you see
- A “free trial” that asks for a credit card and rejects prepaid or debit cards (SERNAC, 2021, p. 29).
- A service that looks like a one-off payment and renews every year; the detail sits behind a “learn more” link (Mathur et al., 2019, p. 14).
How to check. Before paying, look for three things: whether it renews, how much it will charge and when. If any of them is not visible, note it. Asking for a card is not enough to call it a dark pattern; SERNAC treats it as a signal (p. 29), but the proof is that the renewal is not disclosed.
Evidence. Mathur et al.: 14 cases, several combined with a roach motel (Table 1, p. 12; p. 14). SERNAC: 2 stores (2021, p. 16).
Can it be found by searching text? No. SERNAC left it out of its automated search because it needs manual review: simulating the purchase, looking at colors or reading the whole offer (2022, Table 3, p. 9).
Bias (hypothesis). Mathur et al. do not assign one (Table 1, p. 12).
Related: Roach motel
Social engineering
Presenting options or information that lean on social pressure or cognitive biases to get the person to act (Gray et al., 2024, p. 19). The 2021 report by SERNAC, Chile's national consumer protection agency, groups the first four below as “Señales de urgencia y escasez” (urgency and scarcity signals), found in 23 stores (p. 16). They are separated here, with the names from SERNAC's 2022 report (Table 1, pp. 4–5), because each one is tested differently.
Countdown timer
What it is. Shows a clock saying an offer is about to expire, even though the clock is fake, disappears or resets on its own. As a result, the person feels an urgency that is not warranted (Gray et al., 2024, p. 20).
What you see
- A clock in hours, minutes and seconds next to the price or in a banner, with labels such as “Oferta al límite” (offer at its limit) or “Oferta imperdible” (unmissable offer) (SERNAC, 2021, pp. 19–20).
How to prove it deceives. Note the time the clock reaches zero and come back afterwards, and again the next day. It is deceptive if it resets with the same offer or if the offer is still available after it expired (Mathur et al., 2019, p. 15).
Evidence. Mathur et al.: 393 timers, 157 of them deceptive, on 140 sites (p. 15). SERNAC recorded clocks (pp. 19–20) but does not say whether it checked for resets: it counts presence, not deception.
Can it be found by searching text? Partly. SERNAC built 96 typical phrases for “Urgencia”, a group that includes this pattern and others (2022, Table 3, p. 9); a phrase match is a signal to look closer, not proof.
Bias (hypothesis). Scarcity, according to Mathur et al. (Table 1, p. 12).
Related: Limited-time message · Low-stock message
Limited-time message
What it is. Says an offer will end soon without saying when. As a result, the person feels urgency they cannot verify (Gray et al., 2024, p. 20).
What you see
- “Sale ends soon”, with no date or time (Mathur et al., 2019, pp. 15–16).
How to check. Look for the end date in the fine print, in the promotion's conditions and on the terms page. Mathur et al. only counted it when it was in none of those places (pp. 15–16).
Phrases to look for (SERNAC, 2022, pp. 15–17; matching them to this pattern is my own call): «Por tiempo limitado» (for a limited time), «Sólo por hoy» (today only).
Evidence. Mathur et al.: 88 cases (Table 1, p. 12). I did not find an example without a deadline in SERNAC's report: the “¡sólo por 24 hrs.!” (only for 24 hours!) it shows (p. 19) does state a duration.
Can it be found by searching text? Partly. SERNAC built 96 typical phrases for “Urgencia”, a group that includes this pattern and others (2022, Table 3, p. 9); a phrase match is a signal to look closer, not proof.
Bias (hypothesis). Scarcity, according to Mathur et al. (Table 1, p. 12).
Related: Countdown timer
Low-stock message
What it is. Says only a few units are left when that is not true, or without saying how many. As a result, the person buys in a hurry (Gray et al., 2024, p. 19).
What you see
- “Últimas unidades” (last units), the message SERNAC saw most often (p. 19).
- “Solo quedan 2 habitaciones a este precio” (only 2 rooms left at this price) (SERNAC, p. 20).
- “Limited quantities” with no number (Mathur et al., 2019, p. 20).
How to prove it deceives. Come back several times over a few days and note the number. It is suspicious if it drops on a fixed schedule, changes when you reload the page, or the message appears on almost every product (Mathur et al., p. 20).
Phrases to look for (SERNAC, 2022, pp. 15–17; matching them to this pattern is my own call): «Últimas unidades» (last units), «Stock limitado» (limited stock), «Quedan [número] unidades» ([number] units left), «Solo quedan [número]» (only [number] left), «Hasta agotar stock» (while stocks last), «Edición limitada» (limited edition).
Evidence. The most frequent pattern in Mathur et al.: 632 cases. They found 17 deceptive and 49 that gave no quantity (p. 20).
Can it be found by searching text? Partly. SERNAC built 41 typical phrases for “Escasez” (scarcity), a group that includes this pattern and others (2022, Table 3, p. 9); a phrase match is a signal to look closer, not proof.
Bias (hypothesis). Scarcity, according to Mathur et al. (Table 1, p. 12).
Related: High-demand message · Countdown timer
High-demand message
What it is. Says a product is selling fast or is about to sell out, even when that is not true (Gray et al., 2024, p. 19).
What you see
- “Items in your cart are in high demand” (Mathur et al., 2019, p. 20).
How to check. Check whether the message changes with the product. Mathur et al. found that 38 of 47 appeared the same whatever the product or the cart contents (p. 21).
Phrases to look for (SERNAC, 2022, pp. 15–17; matching them to this pattern is my own call): «Alta demanda» (high demand).
Evidence. Mathur et al.: 47 cases (Table 1, p. 12). SERNAC shows no example of this type.
Can it be found by searching text? Partly. SERNAC built 41 typical phrases for “Escasez” (scarcity), a group that includes this pattern and others (2022, Table 3, p. 9); a phrase match is a signal to look closer, not proof.
Bias (hypothesis). Scarcity, according to Mathur et al. (Table 1, p. 12).
Related: Low-stock message · Activity messages
Activity messages
In SERNAC's 2022 report: “Mensajes de actividad”.
What it is. Reports on other people's activity (purchases, visits, carts) with false or misleading data. As a result, the person believes others are buying (Gray et al., 2024, pp. 19–20).
What you see
- Pop-ups such as “Alguien de [district] comenzó a comprar [product] hace 3 minutos” (someone from [district] started buying [product] 3 minutes ago) (SERNAC, 2021, p. 23).
- “¡Apúrate! 2 personas están a punto de comprar este producto” (hurry! 2 people are about to buy this product), repeated across many products (SERNAC, p. 23).
- “35 people added this item to cart”, “90 people have viewed this product” (Mathur et al., 2019, p. 18).
How to prove it deceives. Look at the page source: Mathur et al. found numbers generated at random and messages hard-coded so that they never changed (pp. 18–19). Also check which script draws the message: many come from third-party providers, and some openly advertised fake orders (pp. 22–24).
Phrases to look for (SERNAC, 2022, pp. 15–17; matching them to this pattern is my own call): «Viendo» (viewing), «Viendo esto» (viewing this), «[número] vendidos» ([number] sold), «Compró» (bought), «Alguien en» (someone in), «Interesado» (interested).
Evidence. Mathur et al.: 313 cases, 29 of them deceptive on 20 sites (pp. 18–19). SERNAC: 9 stores, almost always alongside urgency messages (2021, pp. 16 and 23).
Can it be found by searching text? Partly. SERNAC built 17 typical phrases for this pattern (2022, Table 3, p. 9); a phrase match is a signal to look closer, not proof.
Bias (hypothesis). Bandwagon effect, according to Mathur et al. (Table 1, p. 12).
Related: High-demand message · Testimonials of uncertain origin
Testimonials of uncertain origin
What it is. Shows testimonials or endorsements whose origin cannot be verified, or that are partial or false. As a result, the person takes them as real, unbiased opinions (Gray et al., 2024, p. 19).
What you see
- Only positive testimonials, or only top ratings, with no way of knowing how many customers they represent (SERNAC, 2021, p. 21).
- High ratings without the number of reviews behind them (Chen et al., 2026, p. 8).
How to check. Two tests from Mathur et al. (p. 19): see whether the site has a form for submitting testimonials, and search Google for the exact text of one. They found the same testimonials on another site under different names.
Phrases to look for (SERNAC, 2022, pp. 15–17; matching them to this pattern is my own call): «Nuestros clientes dicen» (our customers say), «Excelente servicio» (excellent service), «Excelente producto» (excellent product), «Excelente calidad» (excellent quality), «Muy buena calidad» (very good quality), «Es perfecto» (it's perfect), «Fabuloso» (fabulous).
Evidence. Mathur et al.: 12 cases (Table 1, p. 12). SERNAC: 18 stores (2021, p. 16). SERNAC's criterion is suspicion (p. 21); the two tests above let you go further.
Can it be found by searching text? Partly. SERNAC built 16 typical phrases for this pattern (2022, Table 3, p. 9); a phrase match is a signal to look closer, not proof.
Bias (hypothesis). Bandwagon effect, according to Mathur et al. (Table 1, p. 12).
Related: Activity messages
Confirmshaming
In SERNAC's 2022 report: “Confirma vergüenza”.
What it is. Words the decline option with language or images that shame the person or make them feel guilty. As a result, they change their decision (Gray et al., 2024, p. 20).
What you see
- “No thanks, I like paying full price”, mostly in pop-ups offering a discount in exchange for an email address (Mathur et al., 2019, p. 16).
- When removing optional insurance: “¡No quedes sin protección!” (don't go unprotected!), with “Mantener mis seguros” (keep my insurance) highlighted (SERNAC, 2021, p. 22). SERNAC classified it as visual interference; it has the form of confirmshaming and often comes with a false visual hierarchy.
How to check. Read the decline option without looking at the other one. If it describes the person (“I like paying more”) rather than the action (“no, thanks”), it is confirmshaming. This one needs no proof of deception: you can see it.
Evidence. Mathur et al.: 169 cases (Table 1, p. 12). SERNAC defines it (2021, p. 9) but did not include it among the 10 types surveyed in 2021; it does not appear among the types found in the 2022 manual review (Table 14, pp. 18–19).
Can it be found by searching text? Partly. SERNAC built 45 typical phrases for this pattern (2022, Table 3, p. 9); a phrase match is a signal to look closer, not proof.
Bias (hypothesis). Framing, according to Mathur et al. (p. 16).
Related: Visual interference · Glossary entry